I thought he sounded like he had some horrible cancerous throat disease. xD
But it worked well and fitted the 'character' of batman, and he needed to disguise his real identity.
I felt it was easy enough to understand too. So, no problems from me. =D

The raspiness of his voice might have been a little too distracting in The Dark Knight, but it wasn't without reason. It's probably because this is the first time people have actually HEARD batman speak the way he supposedly speaks in the comics... either way, I just wish they could make it a little less distracting.

true story: so when the movie was about to start and i tell all of my friends, "don't talk to me from this point on" and as soon as batman starts talking my damn friend asked "dude what's wrong with his voice"...

I thought it sounded like he was a heavy smoker with bad asthma. It didn't bother me so much that I disliked the movie. In fact, I thought the movie was amazing, but I couldn't really take Batman seriously in some parts. But whatever...it was one of the very few things I didn't really care for in the movie. Everything else was stellar.